Method of bemoving methanol pbom pybomgneotjs acid liqttob



Dec. 9, 1930. .1. M. coAHRAN METHOD OF REMOVING METHANOL FROMPYROLIGNEOUS ACID LIQUOR .1925 2 Sheets-Sheet l Filed April 23 uw INNfil Patented Dec. 9, 1930 UNITED (STATES PATENT OFFICE JESSE M. COAHRAN,OF COLEGROVE, PENNSYLVANIA METHOD F REMOVING METHANOL FROM PYROLIGNEOU'SACID LIQUOR Application `filed. April 23, 1925. Serial N0. 25,312.

. uor by decantation, most of the soluble oils removed by distillationand the acids neutralized with lime. The methanol as thus recovered isWeak and impure and must be settled, decanted and re-distilled. Otten,then, a considerable portion of the product is insufficiently pure tomeet commercial standards and must be further treated, entailingconsiderable loss and expense. Not only is this process relativelyinvolved and expensive, but it renders impossible the recovery of theacetic acid directly from the liquor.

The present invention has been developed in order to avoid handlingV themethanol at the low concentration involved in the'process ashereinbefore described, to avoid the necessity of the re-distillation ofthe considerable proportion of the acid after it has been concen-Vtrated, to make possible the removal ofcthe methanol Without previousneutralization of the acid so that the acid may be recovered directly,and to attain other advantageous ends as may hereinafter appear.

Briefly this process comprises treating the liquor, preferably afterscreening, With-hot vapor to remove the methanol and then fractionatingthe vapor and methanol to remove the methanol at a fair concentrationwhich leaves behind all but a very small amount of acetic acid so thatthe part removed is crude methanol only. This methanolis notsufficiently pure to meet commercial specifications since it containssome acid and oils in solution.' This impure methanol is then dilutedwith Water to about 20% to 25% (Tralles's scale). At about 27%concentration the oils no longer remain in solution, but

form ya cloudy emulsion. The material is then filtered through a mediumcapable ofvremovacid and the iltrate is then fractionated to therequired strength. The methanol so produced is found to meet standardcrude methanol specifications, practically no fractions from the lastrictionation requiring redistillation. Since this last fractionation isof methanol of fairly high concentration, the further concentrationisrelatively simple and inexpensive.

For a more complete understanding of this invention, reference may behad to the accompanying drawings in which Figure 1 is a diagrammaticrepresentation of apparatus for carrying out the process.

Figure 2 is a section partly broken vaway 65 through one of the filterswhich may be used. l

Referring to Figure l, raw or distilled pyroligneous acid liquorcontaining the methanol is continuously pumped by means of a pump 2 fromstorage tubs, as at 3, through screens 4 to a distributor 5 intermediatethe upper and lower ends of a fractionating column 6. The liquor passingdown Within the collunn is met by a large volume of hot vapors arisingfrom a still or boiling head 7 which is provided with steam coils 8having a large heating capacity. A' thermometer 9 is placed in the vaporpipe 10 between the still and the column 6 to indicate the temperatureof the 80 vapors which should be maintained at about 99 C. to 100o C.,this temperature being above the boiling point of pyroligneous acidcontaining methanol. When the liquor passing down the column meets thehot ascending vaporsthe methanol is boiled and fractioned out and passesout from the column carrylng with it some low boiling oils, Water andsmall amountsof acid. The bulk of the liquor carrying high boiling oils,tars, and most of the acids and water passes through the trapped returnline 11 to the still 7. By means of a trapped line 12 connected to boththe top and bottom of this still to insure the same liquor level in thetrapped line and in the still irrespective of pressure in the still,liquor free from methanol is drawn continuously off from the bottom ofthe still and is trapped through the line 13 to prevent the' passage ofvapors with the liquor. This liq- 10 uor may be fed hot to stills 14,where. it is distilled to remove from it the heavy oils and tars and maythen be condensed in condensers 15 and passed to the storage tubs as at16 where it is in condition to be treated for the direct recovery of theacetic acid, should this be desired. Y

The methanol with vapors passing up through the column 6 is concentratedby fractionation with the help of the partial condenser 20 and is passedthrough the vapor pipe 21 to the condenser 22. Methanol is removed fromthis condenser at a strength of 40% to 65% (Tralless scale) and containsin solution considerable oils and from onefourth to one-half of one percent acid. At this point a portion of the condensed methanol may bereturned to the column 6 through the sight glass 23and the trappedreflux line 24 to aid in fractionation and in building up the strengthof the methanol removed from the column 6.

It is found in practice that the higher the concentration of themethanol removed from the top of the column, the smaller the percentageof acid and oils removed with it, but if the. concentration is raisedtoo high some methanol may find its way down through the still 7 andpass off through the trapped line 13 and be lost.

Condensed methanol from the condenser 22 is drawn off through the sightglass 25 lto an overflow testcup 26. The methanol at this point isclear, all the oils being in solution. Tater is added through the pipe27 to the methanol in the test cup to reduce the percentage of methanolin the mixture to about 20% to 25%. W'hen the concentratin of themethanol is thus reduced below about 27%, (Tralless scale), the oils nolongerremain in the solution but form a cloudy emulsion. From this testcup 26 the liquor passes to a second test cup 28 in order that theconcentration may again be tested and from thence it passes to a settler29. Some of the oils mayl settleout in this settler 29 from Which theymay be withdrawn, but most ofthem pass on to the series of filters at30. It will be notedl the next filter and fills this and if these two`are not of sufficient capacity, the liquor rises to the next filter inthe series the number of filters in use 1s automatically regulated tothe amount of liquor Vto be filtered relative to the capacity of theindividual filters. Thus, as the first filters of the series becomeclogged, those later in the se- By this means ries automatically becomeoperative to take care of the supply of the liquor' to be filtered.These filters contain material which is capable of retaining the cloudyemulsion and neutralizing the acid in the liquor so that the filtrate isa clear methanol liquor of a concentration of from 20% to 25% methanol.

A filtering material which has been found capable of accomplishing theresults desired is calcium carbonate. The crude calcium carbonate whichis the refuse/from acetone plants manufacturing acetone from acetate oflime, has been found quite satisfactory. This' material is sufcientlycoarse grained to make an excellent filtering material, is nearlyinsoluble inwater, and combines chemically with the trace of acids inthe methanol liquor to form acetate of lime which is left in the residuein a still such as that shown at 35 which may be employed to concentratethe methanol from the filters.

It has been found desirable to maintain the filter beds submerged in theliquor during the filtering. operation, consequently the filtrate istaken off through the trapped lines 32 from which it is collected by thereceiving cups 33 and conducted to the storage tank 34. If the filtersare properly functioning it is found that there is no settling of anymaterial in the storage tank; otherwise some times small oily depositswill settle therein. The methanol as drawn off from the storage tank 34may be fractionated and brought up to proper concentration by anysuitable means, either by continuous,or'intermittent process. As' shownthe still 35 has been provided for this purpose, this still beingprovided with a fractionating column 36 and partial and completecondensers 37 and 38,

yrespectively,the concentration being carried out in the well knownmanner, the concentrated methanol being passed to the storage tank 39.It is found that practically all of the product taken from thecondensers of this fractionating column is sufliciently pure to meetcommercial specifications for crude methanol, it being necessary tore-distill almost no fractions to obtain a sufficientlyY pure product.

. The column 6 in which the initial separation of the methanol from theacid liquor takes place may be of any suitable type, though in practiceit has been found desirable to employ a plate construction, the platesbeing provided with fairly large perforations so that the column doesnot readily become clogged. This has been found quite efficient and isreasonably cheap to construct.

While the filters 30 may be constructed in various ways, theconstruction shown in Figure 2 has been found quit-e satisfactory.Referring to this figure, it will be seen that the filter comprises acontainer or tank 40 having above its base 41 a false bottom 42 slattedor formed of hollow tile set on end -45 therein. This bag 44-is providedwith a rope bead 46 at its upper mar in provided at intervals' withloops 47 to acilitate the graspingof the bag by hooks of a hoistingdevice in order that the bag may be removed from the receptacle when itis desired to change the filtering medium. Beneath its upper edge thisbag is held against the inner face of the container as by means of asplit spring ring 48. The liquor to be filtered is supplied to the upperportion of the receptacle through a plpe 5() having a removableextension"51 positioned .inside of the tank, this section 51 havingsupported therefrom a plate V52 to receive the liquor passing from theopen end thereof to break the force of its fall. This plate 52, togetherwith the pipe 51, may he removed to permit the bag and its contents vtobe readily removed from the receptacle when desired, Without obstructhepipe 55 is open to serve as a vent. Leading from the lower end of thepipe 55 is a connection 59 having a control valve 60, this pipe 59 alsolleading to the cup v57. 'The lines 55 and 56 form a trapped outlet forthe liquid so as to maintain the filtering medium 45 entirely submerged,though in actual operation the level of the liquid may be considerablyabove this point, the upper limit of the level of the liquor beingdetermined by the position of the inlet'pipe to the last ilterl of theseries which is in operation at any particular time. AWhen the bagcontaining the filtering medium is to be removed, the filteringreceptacle may be drained by open.- ing the valve 60. Having thusdescribed the process accord ing to this invention and disclosed by wayof example an apparatus for carrying 1t into practice, it should-beunderstood that various modifications and changes might be made Withoutdeparting from the spirit or scope of this invention as defined by theappended claims.

I claim:

1. The method of producing purifiedA methanol which comprises distillingoi methanol from pyroligneous acid liquor and fractionating it to aconcentration above substantially 27% (Tralless scale), diluting theproduct with Watersuiiiciently to cause the dissolved oils to pass outof solution, and then filtering out said oils.

2. The method of producing purified' methanol which comprises subjectingpyro-v ligneous acid liquor to fractional distillation to removetherefrom at a concentration above approximately 27% (Tralless scale)methanol containing oil constituents in solution, diluting thedistillate with Water until such oil constituents go out of solution,and then separating the oil constituents from the dilute methanol.

3. The method of producing purified methanol which comprises subjectingpyroligneous acid liquor to fractional distillation to remove therefromat a concentration ofapproximately 40% (Tralless scale) methanolcontaining oil constituents in solution, diluting the distillate withwater until such oil constituents go out of solution, and thenseparating the oil constituents from the dilu'te methanol.

.4. The method of producing purified methanol which comprises distillingoi methanol from pyroligneous acid liquor and fractionat-ing it to aconcentration :above 27% (Tralless scale), diluting the product WithWater sufficiently to cause its dissolved oils to pass out of solution,then filtering out said oils, and then concentrating the filtrate.

5. The method of producing purified methanol which comprises subjectingpyro- 'ligneous acid liquor to hot vapor to drive methanol containingoil\ constituents,

fractionating the methanol and vapor to conp out of solution, andremoving such constitu- ,l

ents. v

6. The methodof producing purified y methanol which comprises subjectingpyro-7 ligneous acid liquor to hot vapor to drive off methanolcontaining oil constituents, fractionating the methanol and vapor toconcentrate the methanol to above approximateligneous acid liquor to hotvapor to drive off methanol containing oil constituents, fractionatingthe methanol and vapor to concentrate the methanol to aboveapproximately 27% (Tralless scale), diluting with water to -such adegree that the oil constituents go out ligneous acid liquor to hotvapor to ,driveol methanol containing. oil constituents, frac- 4,tionatlng the methanol and vapor to concentrate the .methanol to aboveapproximately 27% (Tralless scale), diluting with water to such a degreethat the oil constituents go out of solution, filtering through calciumcarbonate, and fractionating to concentrate the methanol and leavebehind the neutralized acid constituent.

9. The step in the recovery of methanol from pyroligneous acid liquorwhich comprises removmg therefrom by fractional distillation crudemethanol at a strength above 27% (Tralless scale),

10. The step in the recovery of methanol from pyroligneous acid liquorwhich con1 prises removing therefrom by fractional distillation crudemethanol at a strength of at least 40% (Tralless scale).

In testimony whereof I have aiiixed my signature.

JESSE M. COAHRAN.

